1. Field of the Invention
The present invention relates to an on-chip optical wiring technique for realizing the wiring of, for example, an LSI chip utilizing light, and more particularly, to a laser-induced optical wiring apparatus in which optical wiring is realized by the digital operations of a laser oscillator.
2. Description of the Related Art
Drastic enhancement of the operation speed of LSIs has been achieved by the enhancement of performance of electronic devices, such as bipolar transistors and field effect transistors. However, while the performance of electronic devices is enhanced by the microfabrication of transistors, the wiring resistance or inter-wiring capacitance in the devices is increased as a result of the microfabrication. The increases in the wiring resistance or inter-wiring capacitance are becoming a bottleneck in the increase of the performance of LSIs.
In consideration of such a problem in electric wiring as the above, several optical wiring LSIs, in which light is used to connect elements in the LSIs, have been proposed (see, for example, JP-A H6-132516(KOKAI). Optical wiring is almost free from the dependency of loss upon frequency regardless of whether the current supplied thereto is a direct current or an alternating current of 100 GHz or more, and from disorder in wiring paths due to electromagnetism.
However, such a conventional technique as that of JP-A H6-132516(KOKAI) exhibits significantly low reproducibility and reliability if it is applied to LSIs with an extremely large number of wires. For instance, even if it is assumed that optical wiring is employed only for the uppermost layer (global layer) of LSI wiring, one LSI chip may well include several hundreds of optical wires. In this case, to operate one LSI, it is necessary to operate several hundreds of optical wires with all the wires kept in good condition. In light of the manufacturing yield of LSIs, this means that reproducibility and reliability are required for the production technique, which enable no single defective optical wire to be contained in several tens of thousands to several hundreds of thousands of optical wires produced. Thus, each optical wire for LSIs must have extremely high reproducibility and reliability. To this end, each optical wire must have an extremely simple structure and an extremely small size for highly integration.
Basically, a light-emitting element, optical waveguide and light-receiving element are essential elements for the conventional optical wiring. Accordingly, light-emitting element techniques, light-receiving element techniques and optical waveguide techniques are necessary. It is also necessary to make a complete survey of various techniques including peripheral techniques, such as optical coupling techniques for efficiently optically coupling the light-emitting element to the light-receiving element, and optical transmission system designing techniques. Moreover, those basic elements differ from each other in operation principle, material, structure, processing technique, and hence it is necessary to delicately combine materials and processing techniques to form optical wiring. This process is extremely difficult to realize.
As described above, in conventional optical wiring techniques, since the structural elements are very complex, and various materials must be used to form the elements, problems will easily occur in the stability or reproducibility of the characteristics. Furthermore, it is difficult to reduce the size of the wiring. Thus, the conventional optical wiring techniques include a large number of unsuitable factors for LSI wiring.